This invention relates to a reproducing apparatus of the electrostatographic type and, more particularly, to an optical system which provides, by displacement of various optical components, projection of a continuous range of reduction or enlargement images onto a flat imaging plane.
The prior art includes many examples of machines adapted to copy stationary original documents at a variety of magnification through the use of a scanning optical system. Examplary of patents in this area are U.S. Pat. Nos. 3,476,478 to Rees (add lens); 3,542,467 to Ferguson; 3,614,222 to Post; 3,837,743 to Amemiya; 3,884,574 to Doi et al. and 4,013,361 to Allis.
An important consideration in the type of optical system selected for a particular system is the space alloted within the machine for the optical system. For machines where compactness is a strict requirement, optical systems relying on add lens insertions and on lens and mirror motions towards and away from the photoreceptor are not particularly appropriate.
Efforts to reduce the volume taken up by optical components encounter problems such as the vignetting which occurs when closely spaced optical components interfere with and block light paths thereby reducing the quality of the resulting image. Additional problems which must be addressed by more compact systems are: elimination of the effects of field tilt at any of the various magnification values, and simplification of the motion of those optical components which must be displaced when varying the magnification.